Field of the Technology
The technology presented herein relates to a semiconductor light emitting device on which a semiconductor light emitting element is mounted, and a multiple lead frame for a semiconductor light emitting device.
Description of the Background Art
Conventional semiconductor light emitting devices are disclosed in, for example, Japanese Patent Laying-Open Nos. 2004-274027, 07-235696 and 2002-141558. As shown in FIG. 21, a conventional semiconductor light emitting device includes a lead frame 101 having a main surface 101a, an LED (Light Emitting Diode) chip 104 provided on main surface 101a, a metal wire 105 connecting lead frame 101 and LED chip 104, epoxy resin 106 provided on main surface 101a so as to completely cover LED chip 104 and metal wire 105, and a resin portion 103 provided so as to surround epoxy resin 106.
Resin portion 103 is provided around lead frame 101 by insert molding, for example. Resin portion 103 forms a concave shape on main surface 101a. LED chip 104 is mounted on main surface 101a, with a silver (Ag) paste 107 interposed, to be located inside the concave shape. An electrode formed on the top surface of LED chip 104 is connected to main surface 101a of lead frame 101 via metal wire 105. Epoxy resin 106 is provided on main surface 101a so that LED chip 104 and metal wire 105 are covered and the concave shape is completely filled therewith.
A manufacturing method of the semiconductor light emitting device shown in FIG. 21 is now described. Firstly, plate-like lead frame 101 is processed into a prescribed pattern. Lead frame 101, plated with silver (Ag), is insert-molded in resin portion 103. Thereafter, LED chip 104 is mounted on main surface 101a with silver paste 107 being interposed. LED chip 104 and main surface 101a are electrically connected via metal wire 105. Thereafter, LED chip 104 and metal wire 105 are sealed with epoxy resin 106. Lastly, a lead terminal projecting into the periphery and extending in a prescribed direction is cut so as to be cut away from unnecessary portions of lead frame 101.
Resin portion 103 shown in FIG. 21 plays the role of controlling directivity of light by reflecting the light emitted from LED chip 104 with the concave-shaped sidewall, and also the role of keeping the shape of lead frame 101 having formed in a prescribed pattern. In the step of resin-sealing LED chip 104 and metal wire 105, liquid epoxy resin 106 is dropped into the concave shape formed by resin portion 103 and thereafter cured. However, according to this method, the shape of epoxy resin 106 is limited to the shape of the concave shape formed by resin portion 103, and the optical characteristics by the shape of resin sealing cannot be controlled. Further, dropped epoxy resin 106 tends to be affected by its viscosity, and therefore the filling amount may be varied. Additionally, there are the effect of vaporization of volatile component or cure shrinkage during thermal curing. Therefore, it is difficult to ensure uniform sealing shape.
When epoxy resin 106 and resin portion 103 are adhered to each other as in the conventional technique, since adhesion force between epoxy resin 106 and resin portion 103 is weak, they may possibly be peeled off from each other after molding and the optical characteristics may be impaired. In fact, it has been observed in a long-term aging test that an optical characteristics defect occurs due to peeling between epoxy resin 106 and resin portion 103.
For stabilizing the sealing shape of epoxy resin 106 and for molding into various sealing shapes, molding using a die (die molding) may be employed. In order to perform die molding, it is necessary for the front and rear surfaces of lead frame 101 to be flat. However, as resin portion 103 is protruding on main surface 101a of lead frame 101, clamping of the die is difficult. Japanese Patent Laying-Open No. 2004-274027 also discloses die molding in a state where resin portion 103 protrudes on main surface 101a of lead frame 101 (see paragraph 0059 of the specification of Japanese Patent Laying-Open No. 2004-274027). However, sealing only the periphery of LED chip 104 with epoxy resin 106 is difficult because of the limited clamping region and in consideration of keeping the region for resin gate and runner.
A metal core substrate, a ceramic substrate or the like that can be formed to have a flat surface may be employed for performing die molding. However, while the ceramic substrate is higher in thermal conductivity than a conventional resin substrate such as a glass epoxy substrate (for example, about 20 W/m·K in the case of alumina), the unit price of the substrate is increased. Also, there is a disadvantage that it is easily damaged when clamped by the die. On the other hand, the metal core substrate requires an insulating layer to be provided between the substrate pattern and the metal being the core. This insulating layer reduces the thermal conductivity. That is, there has been no lead frame provided that have the thermal conductivity of the same level as that of a metal frame and that can be die-molded.